The present invention relates to SiH-olefin platinum catalyzed compositions and more specifically relates to SiH-olefin platinum catalyzed compositions having as an inhibitor additive a compound with at last one hydroperoxy radical.
SiH-olefin platinum catalyzed compositions are well known in the art. Such compositions, in one aspect, comprise as the main ingredients vinyl-containing polysiloxane having a treated or untreated filler therein, a hydrogen-containing polysiloxane and finally a platinum catalyst which can be a solid platinum metal deposited on a solid carrier such as, gamma-alumina or a solubilized platinum complex. It is normal in such compositions to package the vinyl polysiloxane, the filler and the platinum catalyst in one package and to package the hydrogen-containing polysiloxane in a second package. When the fabricator or user of the material desires to produce a cured silicone elastomer he mixes the two packages in the specified proportions, fabricates the composition to the desired shape and allows the composition to cure either at room temperature over a period of time or at elevated temperatures in very short periods of time such as, in seconds or minutes.
The above-described compositions which are sold in two components or packages are usually referred to as room temperature vulcanizable silicone rubber compositions and more specifically, SiH-olefin platinum catalyzed room temperature vulcanizable silicone rubber compositions. It is understood that these types of compositions be cured either at room temperature over a perid of time such as, 1 hour or 12 hours after the two components are mixed together or over a very short period of time in seconds or minutes by heating the composition at temperatures above 100.degree. or 200.degree. C.
Such compositions will start curing as soon as the two components are mixed together and will usually cure or at least set in a 1 hour period even at room temperature. Accordingly, it has become desirable to incorporate into such compositions inhibitors which inhibitor additives when added to the composition will retard the curing of the composition when the two components are mixed together for a period of time of at least 12 hours so as to allow the composition to be fabricated to the desired shape before the composition sets. After mixing the two components together of such compositions and prior to their setting prior to the complete cure such that they cannot be molded further, it is desired to have as long a work life as possible. Accordingly, to increase the work life of such SiH-olefin platinum catalyzed composition and specifically compositions comprised of a vinyl-containing polysiloxane and a hydrogen-containing polysiloxane, it has been normal to incorporate into them various types of inhibitors. The function, as stated previously, of such inhibitor is to increase the work life of the composition prior to heating at elevated temperature or allowing the composition to cure at room temperature without impeding or in any way detracting from the final cure and properties of the composition to a silicone elastomer.
One advantage of such inhibitors in the past was to allow the composition to have as prolonged a work life at room temperature by simply heating the composition to allow it to cure in a manner of minutes thus arriving at the cured silicone elastomer fabricated part in an as expeditious and efficient time sequence as possible.
One prominent example of such inhibitors is, for instance, that to be found in the U.S. patent of Kookootsedes et al, U.S. Pat. No. 3,445,420, which discloses the use of acetylenic containing organic polymers and monomers as inhibitors for SiH-olefin platinum catalyzed compositions.
One disadvantage as brought out in Column 2 of the patent is that with the use of such acetylenic radical containing compounds the composition has to be sealed air tight since upon it being exposed to the atmosphere or in case of leaks to the atmosphere the acetylenic compound would evaporate and the inhibiting properties that were desired in the two component composition would be lost. It should be noted that normally SiH-olefin platinum catalyzed compositions which are packaged in two components do not have to be sealed in air tight containers.
Accordingly, it was highly desirable to find inhibitors for SiH-olefin platinum catalyzed compositions which would not necessitate air tight containers for packaging the two components of the SiH-olefin platinum catalyzed composition.
Another difficulty with the acetylenic compounds is that they are very unstable and explosive and accordingly they require careful manufacturing procedures in the preparation of the composition.
An additional defect in such acetylenic inhibitors which was even more prominent was that their effective rate of inhibition was not as high as would be desired.
In the past, the SiH-olefin platinum catalyzed compositions discussed above usually consisted of polysiloxane polymers having a viscosity of anywhere from 1,000 to 500,000 centipoise at 25.degree. C, so that such polymers could be manipulated or worked at a much more efficient rate than was possible with higher viscosity polymers in terms of the work life of the prior art compositions and in terms of the effectiveness of the prior art inhibitors.
Accordingly, it was highly desirable to produce or develop a high viscosity SiH-olefin platinum catalyzed composition where the polymers, at least the base vinyl-containing polymer, would have a viscosity of anywhere from 1,000,000 to 200,000,000 centipoise at 25.degree. C, since such high viscosity polymers would have higher tensile strengths. Such compositions would open a whole range of new uses for SiH-olefin platinum catalyzed compositions.
The difficulty with the developing of such high viscosity SiH-olefin platinum catalyzed compositions was that they normally had to be worked on a mill after the two ingredients were mixed together or in some other apparatus requiring extended work lives of at least 12 hours. Accordingly, in the past when such high viscosity SiH-olefin platinum catalyzed compositions were attempted the high viscosity material would cure on the mill upon the two components being mixed and the composition being worked to fabricate a product. An attempt to find proper inhibitors for such high viscosity SiH-olefin platinum catalyzed compositions did not meet with much success.
The comments with respect to the ineffectiveness of the prior art inhibitors applies to that therein disclosed in the above 3,445,420 patent with respect to such high viscosity compositions.
In another aspect, it was highly desirable to produce SiH-olefin platinum catalyzed compositions which could be prepared both for low viscosity materials and high viscosity materials that could be prepared in a one-component system, that is, be prepared with an inhibitor in the composition which would inhibit the cure of the composition for prolonged periods of time such as, 4 to 6 months. The purchaser of the material could then take the one-component material, whether of high or low viscosity, form the desired product from such composition and then by simply heating it at elevated temperatures to degrade the inhibitor would result in curing of the composition in a matter of minutes to produce the desired fabricated silicone elastomer part.
Accordingly, the prior art inhibitors were not effective enough to produce a work life of sufficient duration for high viscosity SiH-olefin platinum catalyzed room temperature vulcanizable silicone rubber compositions and were not effective enough to produce one-component SiH-olefin platinum catalyzed compositions.
Accordingly, it is one object of the present invention to provide an inhibitor for SiH-olefin platinum catalyzed compositions which is not susceptible to degradation or evaporation upon being exposed to the atmosphere.
It is another object of the present invention to provide an inhibitor for SiH-olefin platinum catalyzed compositions which is relatively stable compared to the acetylenic inhibitors.
It is an additional object of the present invention to provide an inhibitor for SiH-olefin platinum catalyzed room temperature vulcanizable silicone rubber compositions effective for providing an extended work life both for low viscosity and high viscosity SiH-olefin platinum catalyzed room temperature vulcanizable silicone rubber compositions and which is effective for providing extended shelf times for one-component SiH-olefin platinum catalyzed compositions.
It is yet an additional object of the present invention to provide for a process for producing a SiH-olefin platinum catalyzed room temperature vulcanizable silicone rubber composition with an inhibitor therein which composition has an extended work life both in the case of low viscosity compositions and high viscosity compositions and which compositions has a desirable shelf life in the case when one-component SiH-olefin platinum catalyzed room temperature vulcanizable silicone rubber compositions are desired to be produced.
These and other objects of the present invention are accomplished by means of the disclosure set forth herein below.